The present invention relates to a fluid bearing device which supports an axial member in a non-contact manner by an oil film of a lubricating oil generated in a radial bearing gap, and a dynamic bearing device (a fluid dynamic bearing device) which supports an axial member in a non-contact manner by the action of dynamic pressure of lubricating oil generated in a radial bearing gap.
These bearing devices are ideal for use in information equipment, including the spindle motors for magnetic disk devices such as HDD and FDD, optical disk devices for CD-ROM, CD-R/RW, DVD-ROM/RAM, etc. and magneto-optical disk devices for MD, MO, etc., the polygon scanner motors in laser beam printers (LBP), color wheels for a projector, or small-scale motors for electrical equipment such as axial flow fans.
Speedup, cost reduction, noise reduction, and the like are required of the foregoing various motors, in addition to high rotation accuracy. One of components to determine required performance is a bearing for supporting a spindle of the motor. In recent years, a fluid bearing having superior characteristics in regard to the foregoing required performance is contemplated using, or actually used.
This type of fluid bearing is broadly divided into a so-called dynamic pressure bearing and a so-called cylindrical bearing (a bearing the bearing surface of which is in the shape of a perfect circle). The dynamic pressure bearing is provided with dynamic pressure generation means which makes a lubricating oil in a bearing gap generate dynamic pressure. The cylindrical bearing is not provided with such dynamic pressure generation means.
Taking the case of a fluid bearing device which is installed in a polygon scanner motor of a laser beam printer (LBP), for example, the fluid bearing device is provided with a radial bearing portion for supporting an axial member in a non-contact manner rotatably in a radial direction, and a thrust bearing portion for supporting the axial member rotatably in a thrust direction. As the radial bearing portion, a dynamic pressure bearing is used, which is provided with a groove (a dynamic pressure generating groove) in the inner peripheral surface of a bearing sleeve or the outer peripheral surface of the axial member to generate dynamic pressure. As the thrust bearing portion, for example, a bearing which supports one end face of the axial member in a contact manner by a thrust plate (a so-called pivot bearing) is used.
In the fluid bearing device, the bearing sleeve is fixed in a predetermined position of the inner periphery of a housing, and a seal member is fixed in an opening of the housing, in order to prevent the lubricating oil in the internal space of the housing from leaking to the outside. On the outer periphery of the housing, a substrate on which electronic components for controlling the motor are mounted is fixed by means of swaging, bonding or the like.
The foregoing fluid bearing device which comprises many parts such as the housing, the bearing sleeve, the axial member, the thrust plate, the seal member, and the like, and an effort is under way to increase the processing accuracy and the assembly accuracy of each part, for the purpose of ensuring high bearing performances, which are required in accordance with further increase in the performance of the information equipment. Demand for cost reduction on this type of fluid bearing device, on the other hand, has increasingly become severe in accordance with drop in the price and size of the information equipment.